The invention concerns a hot rolling mill with a flatness measuring roll, which is assigned to at least one roller table positioned before and/or after the stands and which influences the settings of at least one of the stands.
In cold rolling mills, the use of flatness measuring rolls, which influence settings and adjustments of stands to produce stress-free rolled strip, is well known, e.g., to be able to produce unequal rolling forces for the uprights of a stand and/or to produce correcting bending forces. In modern hot rolling processes, strip  less than 1.0 mm is rolled, so the use of flatness measuring rolls would also be suitable here. However, so far they have not been used in hot rolling mills, because, on the one hand, they are relatively sensitive, and, on the other hand, their use in a hot rolling mill train would expose them not only to high temperatures, but also to cooling water, and the resulting high temperature gradients would produce extreme stresses in the roll. In addition, the high incidence of scale places a tremendous amount of stress on the flatness measuring roll and reduces its service life.
The goal of the invention is to design a flatness measuring roll for hot rolling mills in such a way that it is protected, especially from environmental influences.
This goal is achieved by the features specified in claim 1. They make it possible either to move out at least one roller table roll and to move the flatness measuring roll into the resulting gap with its uppermost cylindrical surface line well above the bearing plane of the roller table, and then to lower a holddown roll, or to lower the flatness measuring roll and to fill the resulting gap in the roller table with a roller table roll.
As claim 2 proposes, the flatness measuring roll and the roller table roll can be arranged in a box that can be driven to rotate about an axis in such a way that the flatness measuring roll and the roller table roll can be alternately brought into the working position by rotation, preferably in the same direction. However, as claim 9 proposes, there is also the possibility of arranging the flatness measuring roll and the one or more roller table rolls in a box that can be swiveled about an axis in such a way that the flatness measuring roll and the roller table rolls can be alternately brought into the working position by swiveling them up and down.
Advantageous features and modifications of the invention are described in claims 3 to 8 and 10 to 20.